1. Field of Invention
The present invention relates to a gas generator for use in a restraining device such as an airbag system installed on an automobile.
2. Description of the Related Art
An airbag system that protects an occupant from a collision impact is known as a restraining device installed on a vehicle. The airbag system uses a gas generator that inflates an airbag, and the shape and structure of the gas generator itself are known to have various specifications depending on whether the airbag system is designed for a driver side, a passenger side, or side collision.
Because of a large space between windshield or dashboard and a passenger, the volume of an inflated bag for the passenger side is larger than that of the airbag for the driver side, and has a capacity of 120 L or 150 L. Further, because the gas generator used in the airbag apparatus for the passenger side is typically embedded in a dashboard, the gas generator has a housing of a cylindrical shape that is elongated in the axial direction. DE-A No. 4005768, JP-A No. 6-227357 and JP-A No. 9-226508 disclose a pyrotechnic gas generator having a cylindrical housing elongated in the axial direction.
DE-A No. 4005768 discloses a gas generator 10 including an elongated housing that has an igniter 13 attached to one end portion thereof. The gas generating agent 16 is disposed in both the gas generating agent accommodation space of a comparatively large volume in one end portion of the housing and a smaller-diameter portion formed inside the filter, and a channel 20 of a reduced diameter is formed in the central portion. As a result, the gas generating agent that starts burning from one end of the housing by an ignition device 12 needs some time to burn out to the opposite end. In particular, a reduced diameter channel 20 is formed in the central portion, and such a structure is unsuitable for the propagation and advancement of combustion.
In JP-A No. 6-227357, the ignition ability of a gas generating agent disposed far from an igniter is enhanced by using a flame transfer tube. With this invention, the ignition ability of the gas generating agent disposed far from the igniter can be enhanced, but because the flame transfer tube has to be installed, the loaded amount of the gas generating agent is restricted and the resultant structure is not suitable for size-reducing or increasing the output.
In the structure shown in FIG. 1 of JP-A No. 9-226508, the inside of a cylindrical housing 1 is divided by a hollow cylindrical member 20 into a combustion chamber G having a gas generating agent 4 located therein and a cooling filtration chamber F accommodating a filter 21. The hollow cylindrical member 20 includes a flange portion 20b and a body portion 20e extending inside the filter 21 and having gas passage holes 20a formed therein. The body portion 20e is disposed so as to cover the entire inner side of the filter 21. With the structure described in JP-A No. 9-226508, the inside of the hollow cylindrical member 20 is a space that contains nothing and it is not adapted for downsizing the gas generator. Further, such a structure is not suitable for a gas generator with a high gas discharge amount such as a gas generator for an air bag for a passenger side.